The present application is based on Japanese Patent Application Nos. 2002-083102 and 2002-190106 respectively filed on Mar. 25, 2002 and Jun. 28, 2002, the content of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates in general to an apparatus, a method and a program for controlling an electric motor by feedback control using a state estimator or an observer and an apparatus and a method for controlling an operating speed of an electric motor by feedback control to drive a movable object such that a moving speed of the movable object coincides with a target speed value.
2. Discussion of Related Art
There is known an apparatus arranged to control an electric motor by feedback control using a state estimator. FIG. 21 illustrates an example of a feedback control system using a state estimator. This feedback control system includes a state estimator 0 which estimates a state quantity x representative of an internal state of a movable object A, on the basis of a control input u that is a value of a control signal to be applied to an electric motor M, and a control output y representative of an actual operating state of the movable object A as driven by the electric motor M. The control input u to be applied to the electric motor M is generated on the basis of a product of the estimated state quantity x and a gain g, and a product of the gain g and an integrated error (rxe2x88x92y) between a target value r of a control quantity of the electric motor M and the control output y. According to this feedback control, the operation of the electric motor M is controlled such that the control output y eventually coincides with the target value r.
The operating state of the movable object A is usually detected on an output of an encoder, which is arranged to generate encoder signals as the rotor of the electric motor M is rotated. A count of the encoder signals is used as the control output y of the movable object A. When the control input u applied to the electric motor M is a positive value, the angular velocity of the motor M in its forward or normal operating direction is increased according to an absolute value of the control value u. When the control input u is a negative value, on the other hand, the angular velocity of the motor M in its reverse direction is increased, that is, the angular velocity of the motor M in its forward operating direction is reduced, according to the absolute value of the control input u.
However, the motor control apparatus arranged as described above suffers from a risk of temporary operation of the electric motor M (or the movable object) in the direction opposite to the direction in which the motor M is always operated to operate the movable object in the predetermined direction.
Where the electric motor is turned off immediately after the last encoder signal is generated by the encoder provided to detect the operating state of the movable object, there is a comparatively long time interval between the moment at which the motor is turned on again and the moment at which the next encoder signal is to be generated (at which the first encoder signal is to be generated after the motor is turned on again). Where the motor is turned off immediately before the next encoder signal is to be generated by the encoder, there is a comparatively short time interval between the moment at which the motor is turned on again and the moment at which the next encoder signal is to be generated. Thus, the time interval between the moment when the motor is turned on again and the moment at which the next encoder signal is to be generated varies depending upon the moment at which the motor is turned off at the end of the last operation.
Where there is a comparatively long time interval between the moment at which the motor is turned on again and the moment at which the next or first encoder signal is to be generated, only the state quantity x estimated by the state estimator increases during this comparatively long time interval, so that the control signal input to further increase the angular velocity of the motor is applied to the motor. As a result, the count of the encoder signals and the control output y accordingly increase, so that the count of the encoder signals eventually exceeds a value corresponding to the state quantity x as estimated by the state estimator. Consequently, the control signal input to reduce the angular velocity of the motor is applied to the motor. In a transient period immediately after the moment of starting of the motor, the angular velocity of the motor is not so high. In this transient period, therefore, a relatively large amount of reduction of the angular velocity of the motor as represented by the control signal input may cause a risk that the motor is not merely stopped with its operating velocity being zeroed, but the motor is operated in the opposite direction.
Where there is a comparatively short time interval between the moment at which the motor is turned on again and the moment at which the next or first encoder signal is to be generated, the count of the encoder signals and the control output y increase during this comparatively short time interval before the state quantity x estimated by the state estimator increases, so that the control signal input to reduce the angular velocity of the motor is applied to the motor. As in the case where there is a comparatively long time interval between the next or first encoder signal is to be generated after the motor is turned on again, a relatively large amount of reduction of the angular velocity of the motor as represented by the control signal input may cause a risk that the motor is not merely stopped, but the motor is operated in the opposite direction.
After the electric motor is thus operated in the opposite direction, the state quantity x estimated by the state estimator becomes larger than a value corresponding to the count of the encoder (the control output y), so that control signal input to increase the angular velocity of the motor is applied to the motor, whereby the operation of the motor in the opposite direction is terminated in a short time. However, the temporary operation of the motor in the direction opposite to the direction of the normal operation of the motor results in a temporary operation of the movable object in the opposite direction, leading to a considerable amount of vibration of the motor and the movable object.
Where the movable object is a paper feeding mechanism arranged to feed a paper in a printer, the temporary operation of the motor in the opposite direction causes the paper to be fed in the reverse direction during the operation of the paper feeding mechanism to feed the paper in the predetermined forward direction, thus giving rise to a risk of deterioration of accuracy of positioning of the paper.
In a serial printer (e.g., an ink-jet printer) wherein a printing head performs a printing operation on a sheet of paper while the printing head is moved relative to the sheet of paper, a carriage carrying the printing head is moved by a carriage drive motor. To assure high accuracy of positioning of images printed on the sheet of paper, the moving speed of the carriage is required to be controlled with high accuracy, within a predetermined printing area of the sheet of paper. To this end, the moving speed of the carriage is detected by a suitable detector such as an encoder, and an electric current to be applied to the carriage drive motor (CR motor) is controlled according to a suitable control algorithm such as a PID control algorithm such that the detected moving speed of the carriage coincides with a predetermined target speed value, so that a torque generated by the CR motor to drive the carriage is controlled.
In the PID control, control quantities in the form of a proportional control quantity, an integral control quantity and a differential control quantity are calculated on the basis of the detected moving speed of the carriage or a speed error between the detected moving speed and the target speed value. Of these control quantities, the differential control quantity is used to control the electric motor, so as to reduce an influence of an external disturbance of a transient or instantaneous nature.
Where the moving speed of the carriage is detected in a discontinuous or discrete manner, the moving speed used to calculate the control quantities is not updated until the next speed detecting signal is generated. That is, although the actual moving speed has been changed, the moving speed used to calculate the control quantities is kept constant at the last detected value. Thus, the electric motor cannot be controlled adequately so as to reflect the actual moving speed of the carriage.
Described more specifically, where an external disturbance (a variation in the moving speed) is detected by a continuous system (analog system), a derivative response (differential control quantity) has a waveform wherein the differential control quantity abruptly changes upon generation of the external disturbance, as indicated in FIG. 22A. Where the external disturbance is detected by a discrete system (digital system), the derivative response is held constant until the next speed detecting signal is generated, as indicated in FIG. 22B.
A possibility of inadequate control of the moving speed increases with an increase in the detecting interval. The inadequate control includes an overshoot that the actual moving speed becomes considerably higher than the target speed, and an oscillation of the moving speed which is an oscillatory change of the moving speed to and from the target speed. In FIG. 22B, the waveforms of derivative responses 1, 2 and 3 are obtained where the detecting interval is relatively short, medium and long, respectively.
By shortening the detecting interval, it is possible to shorten the time period during which the control quantities are inadequately calculated on the basis of the detected moving speed which is different from the actual moving speed. This arrangement may reduce the possibility of inadequate control of the motor.
However, the shortening of the detecting interval is limited, and does not make it possible to sufficiently reduce the possibility of the inadequate control of the motor. Further, even where the detecting interval is shortened, the actual moving speed of the carriage when the motor is controlled on the basis of the differential control derivative calculated upon generation of the instantaneous external disturbance changes in a time shorter than the shortened detecting interval, so that there is a high possibility that the control quantities become inadequate before the next speed detecting signal is generated.
It is a first object of the present invention to minimize a risk of a temporary operation of an electric motor or a movable object in a direction opposite to a predetermined direction in which the motor or movable object is to be normally operated. It is a second object of this invention to minimize an influence of an instantaneous external disturbance which would cause an inadequate control of an electric motor where a moving speed of a movable object moved by the electric motor is detected by a discrete or digital system. The first or second object may be achieved according to any one of the following modes of the present invention in the form of a motor control apparatus, a motor control method or a motor control program, each of which is numbered like the appended claims and depends from the other mode or modes, where appropriate, for easier understanding of technical features disclosed in the present application and possible combinations of those features. However, it is to be understood that the invention is not limited to those technical features or combinations thereof, and that any one of a plurality of technical features described below with respect to any one mode of the invention may be a subject matter of the present invention, without the other technical feature or features being combined with that one technical feature.
(1) An apparatus for controlling an electric motor provided to drive a movable object, comprising:
a target inputting portion operable to input a target value for controlling a motion of the movable object by the electric motor;
a detector operable to detect one of the motion of the movable object or a motion of the electric motor;
a first signal generator operable to generate a first control signal on the basis of an output of the detector and the target value input by the target inputting portion;
an estimator operable to estimate a state quantity indicative of a state of the motion of the movable object, on the basis of the output of the detector and a motor control signal applied to the electric motor;
a second signal generator operable to generate a second control signal on the basis of the state quantity estimated by the estimator;
a motor-control-signal generator operable to generate the motor control signal on the basis of the first control signal and the second control signal; and
a rectified-input applying portion operable when the motor control signal requires the electric motor to be operated so as to operate the movable object in an opposite direction opposite to a predetermined direction, the rectified-input applying portion rectifying the motor control signal so as to limit the motion of the movable object in the above-indicated opposite direction, and applying the rectified motor control signal to the electric motor.
In the motor control apparatus constructed according to the above mode (1) of the present invention, the rectified-input applying portion is operated when the motor control signal generated by the motor-control-signal generator requires the electric motor to be operated so as to operate the movable object in the direction opposite to the predetermined or desired direction, so that the motor control signal rectified by the rectified-input applying portion so as to limit the motion of the movable object in the opposite direction is applied to the electric motor. Thus, the present motor control apparatus makes it possible to minimize a risk of a temporary motion of the movable object in the direction opposite to the predetermined or desired direction.
The above-indicated predetermined or desired direction of operation of the movable object is a direction in which the movable object is to be operated in a normal state, or a direction in which the movable object is designed to be operated.
The detector is provided to detect the motion of the movable object or electric motor, and may include a rotary or linear encoder. Where the encoder is used, encoder signals generated by the encoder are counted, and a count of the encoder signals may be used as an output of the detector indicative of the motion of the movable object or electric motor.
The motor-control-signal generator is arranged to generate the motor control signal to be applied to the electric motor, on the basis of the first control signal generated by the first signal generator and the second control signal generated by the second signal generator. The motor-control-signal generator may be arranged such that when one of the first and second control signals is not present, the motor control signal is generated on the basis of only the other of the first and second control signals.
The rectified-input applying portion is arranged to rectify or adjust the motor control signal so as to limit or restrict the motion of the movable object in the opposite direction, and apply the thus rectified or adjusted motor control signal to the electric motor. With the electric motor controlled according to the rectified motor control signal, the motion of the movable object in the direction opposite to the predetermined or desired direction is limited or restricted. For instance, the rectified-input applying portion is arranged to rectify the motor control signal, so as to prevent or inhibit a rotary motion of the electric motor in the direction opposite to the predetermined direction. The rectified-input applying portion may be arranged to apply the rectified motor control signal directly to the electric motor, or indirectly to the electric motor through a suitable motor driver circuit provided to drive the electric motor.
The present motor control apparatus wherein the rectified-input applying portion is operable to limit the motion of the movable object in the direction opposite to the predetermined direction may be modified such that the rectified-input applying portion is operable when the motor control signal requires the electric motor to be operated so as to operate the movable object in a direction different or other than the predetermined direction, so that the rectified motor control signal is applied to the electric motor so as to limit the motion of the movable object in the direction other than the predetermined direction.
(2) An apparatus according to the above mode (1), wherein the rectified-input applying portion applies to the electric motor the motor control signal as generated by the motor-control-signal generator, when the motor control signal requires the electric motor to be operated so as to operate the movable object in the predetermined direction.
In the motor control apparatus according to the above mode (2) of the invention, the motor control signal as generated by the motor-control-signal generator is applied to the electric motor when the motor control signal requires the electric motor to be operated so as to operate the movable object in the predetermined direction.
The operation of the rectified-input applying portion to rectify the motor control signal which requires the electric motor to be operated so as to operate the movable object to be operated in the opposite direction may be always performed after an initiation of the operation of the electric motor. However, the electric motor may be required to be operated so as to operate the movable object in the opposite direction opposite to the predetermined direction. For example, the electric motor may be controlled so as to activate the movable object in the opposite direction, when the motion of the movable object in the predetermined direction at a relatively high speed is stopped or terminated, by applying to the electric motor the motor control signal that causes the application of a plugging brake to the electric motor for braking the movable object to decelerate its motion. In view of this situation, the rectified-input applying portion is preferably arranged according to the following mode (3):
(3) An apparatus according to the above mode (1) or (2), wherein the rectified-input applying portion is operable for a predetermined time period after a moment of initiation of an operation of the electric motor, and when the motor control signal requires the electric motor to be operated so as to operate the movable object in the direction opposite to the predetermined direction.
In the motor control apparatus according to the above mode (3), the motor control signal is rectified for only the predetermined time period after the moment of initiation of the electric motor. A motion of the movable object in the opposite direction generally takes place in an initial or transient time period immediately after the moment of initiation of the operation of the electric motor. In view of this, it is desirable to set this transient time period as the time period during which the rectified-input applying portion is held operable to rectify the motor control signal for limiting the motion of the movable object in the opposite direction. This arrangement permits a plugging brake to be applied to the electric motor as needed, after the transient period has expired.
Namely, after the initial or transient time period immediately after the moment of initiation of the operation of the electric motor has expired, the rectified-input applying portion is inoperable to rectify the motor control signal, so that the electric motor can be braked by application of a plugging brake thereto, so that the movable object can be rapidly decelerated and stopped.
The time period during which the motor control signal so as to limit the motion of the movable object in the opposite direction is rectified by the rectified-input applying portion may be detected by measuring a time after the moment of initiation of the electric motor, or by comparing the output of the detector with a predetermined threshold value. Further, this time period may be either a constant time during or may be changed depending upon a suitable parameter, as in the apparatus according to the following mode (4):
(4) An apparatus according to the above mode (3), further comprising a rectifying-time-period changing portion operable to change the time period depending upon the target value.
In the motor control apparatus according to the above mode (4), the rectified-input applying portion is held operable to rectify the motor control signal for the time period which varies with the target value inputted by the target inputting portion.
Generally, the speed of motion of the movable object (or the angular velocity of the electric motor) is determined by the target value inputted by the target inputting portion. Namely, where the target value is relatively large, that is, where the amount of motion of the movable object (or the amount of operation of the electric motor) is relatively large, the speed of motion of the movable object (or the angular velocity of the electric motor) is accordingly high. Where the target value is relatively small, that is, where the amount of motion of the movable object (or the amount of operation of the electric motor) is relatively small, on the other hand, the speed of motion of the movable object (or the angular velocity of the electric motor) is accordingly low.
It is also noted that the moment at which the motor control signal requires the electric motor to be operated so as to operate the movable object in the direction opposite to the predetermined direction in the transient period immediately after the moment of initiation of the operation of the electric motor is advanced with an increase in the speed of motion of the movable object (in the angular velocity of the electric motor). It is further noted that the amount of motion of the movable object (or the amount of motion of the electric motor) until the control signal requires the electric motor to be operated so as to operate the movable object in the opposite direction increases with an increase in the speed of motion of the movable object (or the angular velocity of the electric motor).
It follows from the above analysis that the moment at which the motor control signal requires the electric motor to be operated so as to operate the movable object in the opposite direction is advanced with an increase in the target value inputted by the target inputting portion, and that the amount of motion of the movable object (or the amount of operation of the electric motor) until the motor control signal requires the electric motor to be operated as indicated above increases with an increase in the target value.
It follows from the above analysis that where the time period during which the rectified-input applying portion is operable to rectify the motor control signal is detected by measuring a time after the moment of initiation of the operation of the electric motor, for example, the rectifying-time-period changing portion may be arranged to change the time period such that the time period decreases with an increase in the target value inputted by the target inputting portion, so that the motor control signal can be rectified until the amount of operation of the electric motor has increased to a predetermined constant value irrespective of the target value. Where the above-indicated timer period expires when the value represented by the output of the detector has reached a threshold value, on the other hand, the threshold value may be changed so as to increase with an increase in the target value, so that the motor control signal can be rectified for the predetermined time period irrespective of the target value.
(5) An apparatus according to any one of the above modes (1)-(4), wherein the first signal generator includes an integrating portion operable to integrate an error between the target value and a value represented by the output of the detector, and a first-gain multiplying portion operable to multiply the error integrated by the integrating portion, by a predetermined first gain,
and wherein the second signal generator includes a second-gain multiplying portion operable to multiply the state quantity estimated by the estimator, by a predetermined second gain.
In the motor control apparatus according to the above mode (5), the first signal generator, the second signal generator and the estimator cooperate to effect a feedback control of the electric motor such that the value represented by the output of the detector coincides with the target value inputted by the target inputting portion.
The time period during which the rectified-input applying portion is held operable to rectify the motor control signal so as to limit the motion of the movable object may be changed on the basis of not only the target value but also any other suitable parameter, as in the following mode (6):
(6) An apparatus according to the above mode (5), wherein the rectified-input applying portion is operable for a predetermined time period after a moment of initiation of an operation of the electric motor, and when the motor control signal requires the electric motor to be operated so as to operate the movable object in the direction opposite to the predetermined direction, the apparatus further comprising:
a gain changing portion operable to change the first gain used by the first-gain multiplying portion; and
a rectifying-time-period changing portion operable to change the time period depending upon the target value and the first gain.
In the motor control apparatus according to the above mode (6), the time period during which the rectified-input applying portion is held operable to rectify the motor control signal is changed depending upon not only the target value inputted by the target inputting portion, but also the first gain used by the first-gain multiplying portion.
As discussed above, the speed of the motion of the movable object (or the angular velocity of the electric motor) increases with an increase in the target value inputted by the target inputting portion, that is, with an increase in the amount of the motion of the movable object (or the amount of operation of the electric motor). In this respect, it is noted that the speed of the motion of the movable object (or the angular velocity of the electric motor) increases with the first gain used by the first-gain multiplying portion.
It follows from the above fact that where the time period during which the rectified-input applying portion is operable to rectify the motor control signal is detected by measuring a time after the moment of initiation of the operation of the electric motor, for example, the rectifying-time-period changing portion may be arranged to change the time period such that the time period decreases with an increase in the first gain used by the first-gain multiplying portion, so that the motor control signal can be rectified for the predetermined time period irrespective of the target value. Where the above-indicated timer period expires when the value represented by the output of the detector has reached a threshold value, on the other hand, the threshold value may be changed so as to increase with an increase in the first gain, so that the motor control signal can be rectified until the amount of operation of the electric motor has increased to a predetermined constant value irrespective of the target value.
The time period during which the rectified-input applying portion is held operable to rectify the motor control signal so as to limit the motion of the movable object may be changed on the basis of not only the target value but also any other suitable parameter other than the first gain indicated above, as in the following mode (7):
(7) An apparatus according to the above mode (5) or (6), wherein the rectified-input applying portion is operable for a predetermined time period after a moment of initiation of an operation of the electric motor, and when the motor control signal requires the electric motor to be operated so as to operate the movable object in the direction opposite to the predetermined direction, the apparatus further comprising:
a gain changing portion operable to change the second gain used by the first-gain multiplying portion; and
a rectifying-time-period changing portion operable to change the time period depending upon the target value and the second gain.
In the motor control apparatus according to the above mode (7), the time period during which the rectified-input applying portion is held operable to rectify the motor control signal is changed depending upon not only the target value inputted by the target inputting portion, but also the second gain used by the second-gain multiplying portion.
As discussed above, the speed of the motion of the movable object (or the angular velocity of the electric motor) increases with an increase in the target value inputted by the target inputting portion, that is, with an increase in the amount of the motion of the movable object (or the amount of operation of the electric motor). In this respect, it is noted that the speed of the motion of the movable object (or the angular velocity of the electric motor) increases with the second gain used by the second-gain multiplying portion.
It follows from the above fact that where the time period during which the rectified-input applying portion is operable to rectify the motor control signal is detected by measuring a time after the moment of initiation of the operation of the electric motor, for example, the rectifying-time-period changing portion may be arranged to change the time period such that the time period decreases with an increase in the second gain used by the second-gain multiplying portion, so that the motor control signal can be rectified for the predetermined time period irrespective of the target value. Where the above-indicated timer period expires when the value represented by the output of the detector has reached a threshold value, on the other hand, the threshold value may be changed so as to increase with an increase in the second gain, so that the motor control signal can be rectified until the amount of operation of the electric motor has increased to a predetermined constant value irrespective of the target value.
The detector which is provided to detect the motion of the movable object or electric motor may be arranged as in the following mode (8):
(8) An apparatus according to any one of the above modes (1)-(7), wherein the movable object includes a rotary body rotatable during an operation of the electric motor, and the detector includes a rotary member rotatable with the rotary body.
In the motor control apparatus according to the above mode (8), the detector can detect a rotary motion or position of the rotatable body of the movable object.
For the detector to detect the motion of the electric motor, the detector may be arranged as in the following mode (9):
(9) An apparatus according to any one of the above modes (1)-(7), wherein the detector includes a rotary member attached to a rotary shaft of the electric motor.
In the motor control apparatus according to the above mode (9), the detector can directly detect a rotary motion or position of the electric motor.
(10) An apparatus according to any one of the above modes (1)-(9), wherein the movable object is a rotary body rotated by the electric motor to feed a recording medium in a printer for performing a printing operation on the recording medium.
In the motor control apparatus according to the above mode (10), the rotary body such as a paper feeding roller is effectively prevented from being operated to feed the recording medium in the reverse direction while the printing operation is performed with the recording medium fed in the forward direction.
(11) An apparatus according to any one of the above modes (1)-(10), wherein the detector detects the motion of the movable object or electric motor in a discrete manner.
(12) An apparatus according to any one of the above modes (1)-(11), wherein the motor-control-signal generator includes an intermittent-rotary-motion signal generating portion operable to generate the motor control signal for operating the electric motor to cause an intermittent rotary motion in the predetermined direction.
(13) An apparatus according any one of the above modes (1)-(12), wherein the target inputting portion is operable to input the target value which corresponds to a position at which the movable object is positioned by the electric motor.
(14) A method of controlling an electric motor provided to drive a movable object, comprising the steps of:
inputting a target value for controlling a motion of the movable object by the electric motor;
detecting one of the motion of the movable object or a motion of the electric motor;
generating a first control signal on the basis of the detected motion of the movable object or electric motor and the target value;
estimating a state quantity indicative of a state of the motion of the movable object, on the basis of the detected motion of the movable object or electric motor and a motor control signal applied to the electric motor;
generating a second control signal on the basis of the estimated state quantity;
generating the motor control signal on the basis of the first control signal and the second control signal; and
rectifying the motor control signal, when the motor control signal requires the electric motor to be operated so as to operate the movable object in an opposite direction opposite to a predetermined direction, so as to limit the motion of the movable object in the opposite direction, and applying the rectified motor control signal to the electric motor.
The motor control method according to the above mode (14) has substantially the same advantage as described above with respect to the apparatus according to the above mode (1).
(15) A method according to the above mode (14), wherein the motor control signal is applied to the electric motor, without rectification of the motor control signal, when the motor control signal requires the electric motor to be operated so as to operate the movable object in the predetermined direction.
The motor control method according to the above mode (15) has substantially the same advantage as described above with respect to the apparatus according to the above mode (2).
(16) A method according to the above mode (14) or (15), wherein the motor control signal which requires the electric motor to be operated so as to operate the movable object in the opposite direction is rectified for a predetermined time period after a moment of initiation of an operation of the electric motor.
The motor control method according to the above mode (16) has substantially the same advantage as described above with respect to the apparatus according to the above mode (3).
(17) A method according to the above mode (16), further comprising the step of changing the time period depending upon the target value.
The motor control method according to the above mode (17) has substantially the same advantage as described above with respect to the apparatus according to the above mode (4).
(18) A method according to any one of the above modes (14)-(17), wherein the first control signal is generated by integrating an error between the target value and the detected motion of the movable object or electric motor, and multiplying the integrated error by a predetermined first gain,
and wherein the second control signal is generated by multiplying the estimated state quantity by a predetermined second gain.
The motor control method according to the above mode (18) has substantially the same advantage as described above with respect to the apparatus according to the above mode (5).
(19) A method according to the above mode (18), wherein the motor control signal which requires the electric motor to be operated so as to operate the movable object in the opposite direction is rectified for a predetermined time period after a moment of initiation of an operation of the electric motor, the method further comprising the steps of:
changing the first gain used to generate the first control signal; and
changing the time period depending upon the target value and the first gain.
The motor control method according to the above mode (19) has substantially the same advantage as described above with respect to the apparatus according to the above mode (6).
(20) A method according to the above mode (18) or (19), wherein the motor control signal which requires the electric motor to be operated so as to operate the movable object in the opposite direction is rectified for a predetermined time period after a moment of initiation of an operation of the electric motor, the method further comprising the steps of:
changing the second gain used to generate the second control signal; and
changing the time period depending upon the target value and said second gain.
The motor control method according to the above mode (20) has substantially the same advantage as described above with respect to the apparatus according to the above mode (7).
(21) A method according to any one of the above modes (14)-(20), wherein the movable object is a rotary body rotated by the electric motor to feed a recording medium in a printer for performing a printing operation on the recording medium.
The motor control method according to the above mode (21) has substantially the same advantage as described above with respect to the above mode (10).
(22) A control program executable by a computer system, for controlling an electric motor provided to drive a movable object, by implementing the steps of:
inputting a target value for controlling a motion of the movable object by the electric motor;
detecting one of the motion of, the movable object or a motion of the electric motor;
generating a first control signal on the basis of the detected motion of the movable object or electric motor and the target value;
estimating a state quantity indicative of a state of the motion of the movable object, on the basis of the detected motion of the movable object or electric motor and a motor control signal applied to the electric motor;
generating a second control signal on the basis of the estimated state quantity;
generating the motor control signal on the basis of the first control signal and the second control signal; and
rectifying the motor control signal, when the motor control signal requires the electric motor to be operated so as to operate the movable object in an opposite direction opposite to a predetermined direction, so as to limit the motion of the movable object in the opposite direction, and applying the rectified motor control signal to the electric motor.
The computer system operable according to the control program according to the above mode (22) is identical in function with the motor control apparatus according to the above mode (1), and therefore has substantially the same advantage as described above with respect to the above mode (1).
According to a first preferred form of the control program, the generated motor control signal is applied to the electric motor, without rectification of the motor control signal, when the motor control signal requires the electric motor to be operated so as to operate the movable object in the predetermined direction.
The computer system operable according to the first preferred form of the control program is identical in function with the motor control apparatus according to the above mode (2), and has substantially the same advantage as described above with respect to the apparatus according to the above mode (2).
According to a second preferred form of the control program, the motor control signal which requires the electric motor to be operated so as to operate the movable object in the opposite direction is rectified for a predetermined time period after a moment of initiation of an operation of the electric motor.
The computer system operable according to the second preferred form of the control program, which is identical in function with the motor control apparatus according to the above mode (3), has substantially the same advantage as described above with respect to the apparatus according to the above mode (3).
The above-indicated second preferred form of the control program is preferably arranged to further implement the step of changing the time period depending upon the target value.
The computer system operable according to the above-indicated preferred arrangement of the control program is identical in function with the motor control apparatus according to the above mode (4), and has substantially the same advantage as described above with respect to the apparatus according to the above mode (4).
According to a third preferred form of the control program, the first control signal is generated by integrating an error between the target value and the detected motion of the movable object or electric motor, and multiplying the integrated error by a predetermined first gain,
and wherein the second control signal is generated by multiplying the estimated state quantity by a predetermined second gain.
The computer system operable according to the third preferred form of the control program is identical in function with the motor control apparatus according to the above mode (5) and has substantially the same advantage as described above with respect to the apparatus according to the above mode (5).
The above-indicated third preferred form of the control program is preferably arranged such that the motor control signal which requires the electric motor to be operated so as to operate the movable object in the opposite direction is rectified for a predetermined time period after a moment of initiation of an operation of the electric motor, and to further implement the steps of:
changing the first gain used to generate the first control signal; and
changing the time period depending upon the target value and the first gain.
The computer system operable according to the above-indicated preferred arrangement of the control program is identical in function with the motor control apparatus according to the above mode (6) and has substantially the same advantage as described above with respect to the apparatus according to the above mode (6).
The above-indicated third preferred form of the control program is alternatively or further preferably arranged such that the motor control signal which requires the electric motor to be operated so as to operate the movable object in the opposite direction is rectified for a predetermined time period after a moment of initiation of an operation of the electric motor, and to further implement the method further comprising the steps of:
changing the second gain used to generate the second control signal; and
changing the time period depending upon the target value and said second gain.
The computer system operable according to the above-indicated preferred arrangement of the control program is identical in function with the motor control apparatus according to the above mode (7) and has substantially the same advantage as described above with respect to the apparatus according to the above mode (7).
The control program is available on the motor control apparatus described above with respect to the above modes (1)-(13), and to the user of the apparatus, through a floppy disc (FD), a CD-ROM, program codes stored in a read-only-memory (ROM), or any other data storage medium, or an internet or any other communication line or network.
The computer system used to execute the control program described above may be a computer system incorporating a CPU and provided in the motor control apparatus described above with respect to the above modes (1)-(13), or may alternatively be connected to the motor control apparatus through a wire or wireless communication system.
(23) A control program according to the above mode (22), wherein the movable object is a rotary body rotated by the electric motor to feed a recording medium in a printer for performing a printing operation on the recording medium.
The computer system operable according to the control program according to the above mode (23) is identical in function with the motor control apparatus according to the above mode (10), and has substantially the same advantage as described above with respect to the above mode (10).
(24) A data storage medium accessible by a computer system and storing a control program according to the above mode (22).
(25) A printer including a paper-feeding electric motor, and a paper-feeding mechanism having a rotary body rotatable by the paper-feeding electric motor to feed a recording medium, during a printing operation on the recording medium, the printer comprising cough
a target inputting portion operable to input a target value for controlling a rotary motion of the rotary body by the paper-feeding electric motor;
a detector operable to detect one of the rotary motion of the rotary body and a rotary motion of the paper-feeding electric motor;
a first signal generator operable to generate a first control signal on the basis of an output of the detector and the target value input by the target inputting portion;
an estimator operable to estimate a state quantity indicative of a state of the rotary motion of the rotary body, on the basis of the output of the detector and a motor control signal applied to the paper-feeding electric motor;
a second signal generator operable to generate a second control signal on the basis of the state quantity estimated by the estimator;
a motor-control-signal generator operable to generate the motor control signal on the basis of the first control signal and the second control signal; and
a rectified-input applying portion operable when the motor control signal requires the paper-feeding electric motor to be operated so as to rotate the rotary body in an opposite direction opposite to a predetermined direction, the rectified-input applying portion rectifying the motor control signal so as to limit the rotary motion of the rotary body in the opposite direction, and applying the rectified motor control signal to the paper-feeding electric motor.
In the printer according to the above mode (25), the rotary body such as a paper feeding roller is effectively prevented from being rotated to feed the recording medium in the reverse direction while the printing operation is performed with the recording medium fed in the forward direction.
(26) A printer according to the above mode (25), further including a carriage-drive electric motor, a carriage movable by the carriage-drive electric motor in a direction intersecting a direction of feeding of the recording medium by the paper feeding mechanism, and a printing head carried by the carriage and operable to perform the printing operation on the recording medium, the printer further comprising:
a speed detector operable to detect a moving speed of the carriage in a discrete manner;
a speed-control-error calculator operable to calculate a speed control error between the moving speed detected by the speed detector and an externally commanded target speed value;
a speed-control-quantity calculator operable to calculate speed control quantities including a proportional control quantity proportional to the detected moving speed or the speed control error, and an integral control quantity proportional to an integral of the speed control error;
a differential-control-quantity calculator operable to calculate a differential control quantity proportional to a derivative or an amount of change per unit time of the detected moving speed or the speed control error;
a control-command-value determining portion operable to determine a control command value for operating the carriage-drive electric motor to move the carriage at the target speed value, on the basis of the speed control quantities and the differential control quantity, the electric motor being controlled according to the control command value such that the detected moving speed coincides with the target speed value; and
a differential-control-quantity compensating portion operable after a predetermined derivative effective time after each point of time at which the differential control quantity is updated by the differential-control-quantity calculator on the basis of the moving speed detected by the speed detector, to compensate the differential control quantity such that the compensated differential control quantity is smaller than the differential control quantity as updated by the differential-control-quantity calculator, the derivative effective time being shorter than a period of detection of the moving speed by the speed detector.
The printer according to the above mode (26) has an advantage as described below with respect to the following mode (27), as well as the advantage described above with respect to the above mode (25).
(27) An apparatus for feedback-controlling an operating speed of an electric motor provided to drive a movable object, comprising:
a speed detector operable to detect a moving speed of the movable object in a discrete manner;
a speed-control-error calculator operable to calculate a speed control error between the moving speed detected by the speed detector and an externally commanded target speed value;
a speed-control-quantity calculator operable to calculate speed control quantities including a proportional control quantity proportional to the detected moving speed or the speed control error, and an integral control quantity proportional to an integral of the speed control error;
a differential-control-quantity calculator operable to calculate a differential control quantity proportional to a derivative or an amount of change per unit time of the detected moving speed or the speed control error;
a control-command-value determining portion operable to determine a control command value for operating the electric motor to move the movable object at the target speed value, on the basis of the speed control quantities and the differential control quantity, the electric motor being controlled according to the control command value such that the detected moving speed coincides with the target speed value; and
a differential-control-quantity compensating portion operable after expiration of a predetermined derivative effective time after each point of time at which the differential control quantity is updated by the differential-control-quantity calculator on the basis of the moving speed detected by the speed detector, to compensate the differential control quantity such that the compensated differential control quantity is smaller than the differential control quantity as updated by the differential-control-quantity calculator, the derivative effective time being shorter than a period of detection of the moving speed by the speed detector.
In the motor control apparatus according to the above mode (27), the differential-control-quantity compensating portion which is operable after the predetermined derivative effective time has expired is arranged to reduce the differential control quantity as calculated by the differential-control-quantity calculator, so that the reduced differential control quantity is used by the control-command-value determining portion to determine the control command value after expiration of the derivative effective time.
In the motor control apparatus according to the above mode (27), therefore, the weight of the derivative control quantity used to determine the control command value is not held constant during an entire length of a time period following each point of time at which the differential control quantity is updated by the differential-control-quantity calculator. Namely, the differential control quantity as calculated or updated by the differential-control-quantity calculator is used without compensation thereof before expiration of the predetermined derivative effective time, and is reduced to a suitably reduced value after the expiration of the derivative effective time.
In the motor control apparatus according to the above mode (27), the electric motor is controlled according to the control command value determined by using the differential control quantity as calculated by the differential-control-quantity calculator, until the predetermined derivative effective time has expired. Accordingly, the electric motor can be controlled with high stability, even in the presence of an instantaneous external disturbance or noise. After the derivative effective time has passed, however, the differential control quantity as reduced by the differential-control-quantity compensating portion is used to determine the control command value, making it possible to reduce a risk of inadequate determination of the control command value and prevent consequent inadequate control of the motor involving an overshoot or other drawback, during a time period between the moment of expiration of the derivative effective time and the next point of time at which the moving speed is detected or at which the differential control quantity is updated.
(28) An apparatus according to the above mode (27), wherein the differential-control-quantity compensating portion reduces the differential control quantity as a time passes after the expiration of the predetermined derivative effective time.
In the motor control apparatus according to the above mode (28) wherein the differential control quantity is reduced as the time passes after the expiration of the derivative effective time, the weight of the derivative control quantity used to determine the control command value is gradually reduced.
The arrangement according to the above mode (27) therefore permits optimization of the control command value and assures adequate control of the electric motor, even where it takes a relatively long control response time until the actual moving speed of the movable object coincides with the target speed value.
(29) An apparatus according to the above mode (27), wherein the differential-control-quantity compensating portion reduces the differential control quantity to a predetermined constant value.
In the motor control apparatus according to the above mode (29), the weight of the differential control quantity used to determine the control command value can be rapidly reduced after the expiration of the predetermined derivative effective time.
The arrangement according to the above mode (29) permits optimization of the control command value where it takes a relatively short control response time until the actual moving speed of the movable object coincides with the target speed value, after a control of the electric motor according to the control command value influenced by an instantaneous external disturbance.
Where the actual moving speed of the movable object can coincide with the target speed value in a relatively short control response time, for example, the differential control quantity is preferably reduced to zero after the expiration of the derivative effective time. Where the actual moving speed can be made close to the target speed value in a relatively short control response time, but a comparatively small error is left therebetween, the differential control quantity is preferably reduced to a predetermined percentage (e.g., about 20%) of the value as calculated by the differential-control-quantity calculator.
(30) An apparatus according to any one of the above modes (27)-(29), wherein the differential-control-quantity calculator calculates the differential control quantity at a predetermined constant time interval.
In the motor control apparatus according to the above mode (30), the differential-control-quantity calculator calculates the differential control quantity, not at a time interval which varies with the moving speed of the movable object, but at the predetermined constant time interval, so that the control command value can be updated at this constant time interval, assuring improved stability of control of the electric motor irrespective of the moving speed of the movable object.
In the motor control apparatus according to the above mode (30) wherein the differential control quantity is updated at the predetermined constant time interval, the electric motor can be controlled with high stability irrespective of whether the moving speed of the movable object is detected at a constant time interval or not.
(31) An apparatus according to any one of the above modes (27)-(30), further comprising a command-signal generator operable to generate a pulse-width-modulation signal for controlling the electric motor, on the basis of the control command value, at a predetermined pulse-width-modulation time interval, and the predetermined derivative effective time is longer than the pulse-width-modulation time interval.
In the motor control apparatus according to the above mode (31) wherein the predetermined derivative effective time is longer than the pulse-width-modulation time interval, the compensation of the differential control quantity does not take place during the pulse-width-modulation time interval, making it possible to prevent a delay in the control response of the electric motor. In particular, the derivative effective time determined to be substantially equal to a multiple of the pulse-width-modulation time interval permits the moment of compensation of the calculated differential control quantity to be substantially coincident with the moment at which the pulse-width-modulation signal is updated by the command-signal generator, so that the control response of the electric motor can be improved while preventing an unnecessary time between the moment of compensation of the differential control quantity and the moment of updating of the pulse-width-modulation signal.
Therefore, the motor control apparatus according to the above mode (31) does not suffer from deterioration of the control response and consequent inadequate control of the electric motor, even where the motor control apparatus is arranged to discontinuously or discretely detect the moving speed of the movable object and control the electric motor by pulse width modulation (PWM control).
(32) An apparatus according to any one of the above modes (27)-(31), further comprising a derivative-effective-time determining portion operable to determine the predetermined derivative effective time depending upon the target speed value.
In the motor control apparatus according to the above mode (32) wherein the derivative effective time is determined depending upon the target speed value of the movable object, which may be changed according to an external signal, the derivative effective time suitably determined depending upon the target speed value permits a suitable change of the weight of the differential control quantity used to determine the control command value, so that the actual moving speed can coincide with the target speed value after generation of an external disturbance.
The motor control apparatus according to the above mode (32) permits the control command value to be suitably determined for adequate control of the electric motor, even where the target speed value is variable.
(33) An apparatus according to any one of the above modes (27)-(32), wherein the movable object is a carriage which is movable by the electric motor and which carries a printing head for performing a printing operation in a printer.
(34) An apparatus according to any one of the above modes (27)-(33), further comprising a constant-target-value determining portion operable to determine a constant value as the externally commanded target speed value.
(35) A method of feedback-controlling an operating speed of an electric motor provided to drive a movable object, comprising the steps of:
detecting a moving speed of the movable object in a discrete manner;
calculating a speed control error between the detected moving speed and an externally commanded target speed value;
calculating speed control quantities including a proportional control quantity proportional to the detected moving speed or the speed control error, and an integral control quantity proportional to an integral of the speed control error;
calculating a differential control quantity proportional to a derivative or an amount of change per unit time of the detected moving speed or the speed control error;
determining a control command value for operating the electric motor to move the movable object at the target speed value, on the basis of the speed control quantities and the differential control quantity, the electric motor being controlled according to the control command value such that the detected moving speed coincides with the target speed value; and
after expiration of a predetermined derivative effective time after each point of time at which the differential control quantity is updated on the basis of the detected moving speed, compensating the differential control quantity such that the compensated differential control quantity is smaller than the updated differential control quantity, the derivative effective time being shorter than a period of detection of the moving speed.
In the motor control method according to the above mode (35), the control command value is determined by using the differential control quantity as calculated or updated, until the predetermined derivative effective time has expired after each point of time at which the differential control quantity is updated. After the derivative effective time has expired, the differential control quantity compensated to a reduced value is used to determine the control command value. In the present motor control method, therefore, the weight of the derivative effective time is not held constant during an entire length of a time period following each point of time at which the differential control quantity is updated. Instead, the weight of the differential control quantity is reduced to a suitably reduced value after the expiration of the derivative effective time.
Namely, the electric motor is controlled according to the control command value determined by using the differential control quantity as calculated, before the expiration of the predetermined derivative effective time. Accordingly, the electric motor can be controlled with high stability such that the actual moving speed of the movable object approaches the target speed value in a relatively short time, even in the presence of an instantaneous external disturbance or noise.
During the derivative effective time, the actual moving speed varies as a result of a control of the electric motor according to the control command value. At the moment when the predetermined derivative effective time has passed, for instance, the actual moving speed is different from the last detected moving speed (closer to the target speed value). Accordingly, the control command value before the moving speed is detected at the next point of time does not reflect the actual moving speed, so that a continued use of the once determined control command value may cause a relatively large amount of deviation of the actual moving speed from the target speed value.
In the present motor control method, however, the differential control quantity is compensated to a suitably reduced value after the expiration of the predetermined derivative effective time, and the control command value is determined by using the thus reduced differential control quantity, making it possible to prevent a significant deviation of the control command value from an optimum value corresponding to the actual moving speed. Thus, the present motor control method makes it possible to reduce a risk of inadequate determination of the control command value during a time period between the moment of expiration of the derivative effective time and the next point of time at which the moving speed is detected or the differential control quantity is updated.
In the motor control method according to the above mode (35), the electric motor is controlled according to the control command value determined by using the differential control quantity as calculated, until the predetermined derivative effective time has expired. Accordingly, the electric motor can be controlled with high stability, even in the presence of an instantaneous external disturbance or noise. After the derivative effective time has passed, however, the differential control quantity is reduced, and the reduced differential-control-quantity compensating portion is used to determine the control command value, making it possible to reduce a risk of inadequate determination of the control command value and prevent consequent inadequate control of the motor involving an overshoot or other drawback, during the time period between the moment of expiration of the derivative effective time and the next point of time at which the moving speed is detected or at which the differential control quantity is updated.
Where it takes a relatively long control response time until the actual moving speed coincides with the target speed value after the electric motor is controlled according to the control command value influenced by an instantaneous external disturbance, rapid reduction of the differential control quantity may give rise to a risk that the actual moving speed does not sufficiently coincide with the target speed value, leading to inadequate control of the electric motor. In view of this risk, the motor control method may be arranged according to the following mode (36).
(36) A method according to the above mode (35), wherein the step of compensating the differential control quantity comprises reducing the differential control quantity as a time passes after the expiration of the predetermined derivative effective time.
In the motor control method according to the above mode (36), the weight of the differential control quantity used to determine the control command value is gradually reduced after the predetermined derivative effective time has expired. This gradual reduction of the weight of the differential control quantity permits optimization of the control command value and assures adequate control of the electric motor, even where it takes a relatively long control response time until the actual moving speed of the movable object coincides with the target speed value.
(37) A method according to the above mode (35), wherein the step of compensating the differential control quantity comprises reducing the differential control quantity to a predetermined constant value.
In the motor control method, the weight of the differential control quantity is relatively rapidly reduced after the expiration of the derivative effective time. This alternative arrangement according to the above mode (37) permits optimization of the control command value where it takes a relatively short control response time until the actual moving speed of the movable object coincides with the target speed value, after a control of the electric motor according to the control command value influenced by an instantaneous external disturbance.
Where the actual moving speed of the movable object can coincide with the target speed value in a relatively short control response time, for example, the differential control quantity is preferably reduced to zero after the expiration of the derivative effective time. Where the actual moving speed can be made close to the target speed value in a relatively short control response time, but a comparatively small error is left therebetween, the differential control quantity is preferably reduced to a predetermined percentage (e.g., about 20%) of the calculated value.
The timing at which the differential control quantity is calculated can be determined as needed. For instance, the differential control quantity may be calculated at the time at which the moving speed of the movable object is detected. Where the period of detection of the moving speed of the movable object varies with the actual moving speed, the timing of calculation of the differential control quantity also varies with the actual moving speed. Accordingly, the point of time at which the control command value is updated also varies with the actual moving speed. When the control command value is updated at a relatively long time interval, in particular, the electric motor cannot be controlled with high stability, due to a relatively long period of control according to the inadequate control command value not reflecting the actual moving speed of the movable object. In view of this drawback, the motor control method is preferably arranged according to the following mode (38).
(38) A method according to any one of the above modes (35)-(37), wherein the step of calculating a differential control quantity comprises calculating the differential control quantity at a predetermined constant time interval.
In the motor control method according to the above mode (38), the differential control quantity is not calculated at a time interval which varies with the moving speed of the movable object, but is calculated at the predetermined constant time interval, so that the control command value can be updated at this constant time interval, assuring improved stability of control of the electric motor irrespective of the moving speed of the movable object.
In the motor control method according to the above mode (38) wherein the differential control quantity is updated at the predetermined constant time interval, the electric motor can be controlled with high stability irrespective of whether the moving speed of the movable object is detected at a constant time interval or not.
Where the electric motor is controlled by pulse width modulation (by PWM control), a pulse-width-modulation signal (PWM control signal) is generated or updated at a predetermined pulse-width-modulation time interval, such that the value of the pulse-width-modulation signal used to control the electric motor is held constant during the period of the pulse-width-modulation signal. If the differential control quantity is compensated during this period, the compensation of the differential control quantity will not be reflected on the pulse-width-modulation signal until the period has expired. If the derivative effective time is determined to be shorter than the pulse-width-modulation time interval, the compensation of the differential control quantity always takes place during the period of the pulse-with-modulation signal. In view of this, the motor control method is preferably arranged according to the following mode (39).
(39) A method according to any one of the above modes (35)-(38), further comprising the step of generating a pulse-width-modulation signal for controlling the electric motor, on the basis of the control command value, at a predetermined pulse-width-modulation time interval, and wherein the step of compensating the differential control quantity comprises compensating the differential control quantity after expiration of the predetermined derivative effective time which is longer than the pulse-width-modulation time interval.
In the motor control method according to the above mode (39) wherein the predetermined derivative effective time is longer than the pulse-width-modulation time interval, the compensation of the differential control quantity does not take place during the pulse-width-modulation time interval, making it possible to prevent a delay in the control response of the electric motor.
In particular, the derivative effective time determined to be substantially equal to a multiple of the pulse-width-modulation time interval permits the moment of compensation of the calculated differential control quantity to be substantially coincident with the moment at which the pulse-width-modulation signal is updated by the command-signal generator in the step of generating the pulse-width-modulation signal, so that the control response of the electric motor can be improved while preventing an unnecessary time between the moment of compensation of the differential control quantity and the moment of updating of the pulse-width-modulation signal.
Therefore, the motor control method according to the above mode (39) does not suffer from deterioration of the control response and consequent inadequate control of the electric motor, even where the motor control apparatus is arranged to discontinuously or discretely detect the moving speed of the movable object and control the electric motor by pulse width modulation (PWM control).
An instantaneous external disturbance may cause a variation in the moving speed of the movable object. In this event, the moving speed is eventually stabilized or converged at the target speed value. As known in the art, a time from a moment of initiation of the variation of the moving speed to the moment at which the moving speed is stabilized at the target speed value varies depending upon various factors (such as the target speed value). Therefore, the optimum value of the derivative effective time varies depending upon the target speed value. Where the target speed value is changed or variable, the use of the constant derivative effective time may cause inadequate control of the electric motor. In view of this drawback, the motor control method is preferably arranged according to the following mode (40).
(40) A method according to any one of the above modes (35)-(39), further comprising the step of determining the predetermined derivative effective time depending upon the target speed value.
In the motor control method according to the above mode (40) wherein the derivative effective time is determined depending upon the target speed value of the movable object, which may be changed according to an external signal, the derivative effective time suitably determined depending upon the target speed value permits a suitable change of the weight of the differential control quantity used to determine the control command value, so that the actual moving speed can coincide with the target speed value after generation of an external disturbance.
(41) A method according to any one of the above modes (35)-(40), wherein the movable object is a carriage which is movable by the electric motor and which carries a printing head for performing a printing operation in a printer.
(42) A control program executable by a computer system, for controlling an electric motor provided to drive a movable object, by implementing the steps of:
detecting a moving speed of the movable object in a discrete manner;
calculating a speed control error between the detected moving speed and an externally commanded target speed value;
calculating speed control quantities including a proportional control quantity proportional to the detected moving speed or the speed control error, and an integral control quantity proportional to an integral of the speed control error;
calculating a differential control quantity proportional to a derivative or an amount of change per unit time of the detected moving speed or the speed control error;
determining a control command value for operating the electric motor to move the movable object at the target speed value, on the basis of the speed control quantities and the differential control quantity, the electric motor being controlled according to the control command value such that the detected moving speed coincides with the target speed value; and
after expiration of a predetermined derivative effective time after each point of time at which the differential control quantity is updated on the basis of the detected moving speed, compensating the differential control quantity such that the compensated differential control quantity is smaller than the updated differential control quantity, the derivative effective time being shorter than a period of detection of the moving speed.
(43) A control program according to the above mode (42), wherein the movable object is a carriage which is movable by the electric motor and which carries a printing head for performing a printing operation in a printer.
(44) A data storage medium accessible by a computer system and storing a control program according to the above mode (42).
(45) A printer including a carriage-drive electric motor, a carriage movable by the carriage-drive electric motor, and a printing head carried by the carriage and operable to perform a printing operation on a recording medium, the printer comprising:
a speed detector operable to detect a moving speed of the movable object in a discrete manner;
a speed-control-error calculator operable to calculate a speed control error between the moving speed detected by the speed detector and an externally commanded target speed value;
a speed-control-quantity calculator operable to calculate speed control quantities including a proportional control quantity proportional to the detected moving speed or the speed control error, and an integral control quantity proportional to an integral of the speed control error;
a differential-control-quantity calculator operable to calculate a differential control quantity proportional to a derivative or an amount of change per unit time of the detected moving speed or the speed control error;
a control-command-value determining portion operable to determine a control command value for operating the electric motor to move the movable object at the target speed value, on the basis of the speed control quantities and the differential control quantity, the electric motor being controlled according to the control command value such that the detected moving speed coincides with the target speed value; and
a differential-control-quantity compensating portion operable after expiration of a predetermined derivative effective time after each point of time at which the differential control quantity is updated by the differential-control-quantity calculator on the basis of the moving speed detected by the speed detector, to compensate the differential control quantity such that the compensated differential control quantity is smaller than the differential control quantity as updated by the differential-control-quantity calculator, the derivative effective time being shorter than a period of detection of the moving speed by the speed detector.
(46) A printer including:
a medium-support member operable to support a recording medium;
a printing head operable to perform a printing operation on the recording medium supported by the medium-support member;
an intermittent-relative-movement device including an electric motor and operable to intermittently move the recording medium and the printing head relative to each other; and
a motor control apparatus operable to control the electric motor,
and wherein the motor control apparatus comprising:
a target inputting portion operable to input a target value for controlling an intermittent relative movement of the recording medium and the printing head;
a detector operable to detect the intermittent relative movement;
a first signal generator operable to generate a first control signal on the basis of an output of the detector and the target value input by the target inputting portion;
an estimator operable to estimate a state quantity indicative of a state of the intermittent relative movement, on the basis of the output of the detector and a motor control signal applied to the electric motor;
a second signal generator operable to generate a second control signal on the basis of the state quantity estimated by the estimator;
a motor-control-signal generator operable to generate the motor control signal on the basis of the first control signal and the second control signal; and
a rectified-input applying portion operable when the motor control signal requires the electric motor to be operated so as to effect the intermittent relative movement in an opposite direction opposite to a predetermined direction, the rectified-input applying portion rectifying the motor control signal so as to limit the intermittent relative movement in the opposite direction, and applying the rectified motor control signal to the paper-feeding electric motor.
(47) A printer according to the above mode (46), wherein the intermittent-relative-movement device comprises at least one rotatable feed roller for contact with the recording medium to feed the recording medium, and a roller rotating device including the electric motor and operable to intermittently rotate the at last one rotatable feed roller.
(48) A printer including:
a medium-support member operable to support a recording medium;
a printing head operable to perform a printing operation on the recording medium supported by the medium-support member;
a continuous-relative-movement device including an electric motor and operable to continuously move the recording medium and the printing head relative to each other; and
a motor control apparatus operable to control the electric motor,
and wherein the motor control apparatus comprising:
a speed detector operable to detect a speed of a continuous relative movement of the recording medium and the printing head in a discrete manner;
a speed-control-error calculator operable to calculate a speed control error between the speed of the continuous relative movement detected by the speed detector and an externally commanded target speed value;
a speed-control-quantity calculator operable to calculate speed control quantities including a proportional control quantity proportional to the detected speed of the continuous relative movement or the speed control error, and an integral control quantity proportional to an integral of the speed control error;
a differential-control-quantity calculator operable to calculate a differential control quantity proportional to a derivative or an amount of change per unit time of the detected speed of the continuous relative movement or the speed control error;
a control-command-value determining portion operable to determine a control command value for operating the electric motor to effect the continuous relative movement at the target speed value, on the basis of the speed control quantities and the differential control quantity, the electric motor being controlled according to the control command value such that the detected speed of the continuous relative movement coincides with the target speed value; and
a differential-control-quantity compensating portion operable after expiration of a predetermined derivative effective time after each point of time at which the differential control quantity is updated by the differential-control-quantity calculator on the basis of the speed of the continuous relative movement detected by the speed detector, to compensate the differential control quantity such that the compensated differential control quantity is smaller than the differential control quantity as updated by the differential-control-quantity calculator, the derivative effective time being shorter than a period of detection of the speed of the continuous relative movement by the speed detector.
(49) A printer according to the above mode (48), wherein the continuous-relative-movement device comprises a carriage which carries the printing head and which is movable in a direction parallel to the medium-support member, and a carriage moving device including the electric motor and operable to move the carriage.
(50)A printer including:
a medium-support member operable to support a recording medium;
a printing head operable to perform a printing operation on the recording medium supported by the medium-support member;
an intermittent-relative-movement device including a first electric motor and operable to intermittently move the recording medium and the printing head relative to each other;
a continuous-relative-movement device including a second electric motor and operable to continuously move the recording medium and the printing head relative to each other;
a first motor control apparatus operable to control the first electric motor; and
a second motor control apparatus operable to control the second electric motor,
wherein the first motor control apparatus comprising:
a target inputting portion operable to input a target value for controlling an intermittent relative movement of the recording medium and the printing head;
a detector operable to detect the intermittent relative movement;
a first signal generator operable to generate a first control signal on the basis of an output of the detector and the target value input by the target inputting portion;
an estimator operable to estimate a state quantity indicative of a state of the intermittent relative movement, on the basis of the output of the detector and a motor control signal applied to the first electric motor;
a second signal generator operable to generate a second control signal on the basis of the state quantity estimated by the estimator;
a motor-control-signal generator operable to generate the motor control signal on the basis of the first control signal and the second control signal; and
a rectified-input applying portion operable when the motor control signal requires the first electric motor to be operated so as to effect the intermittent relative movement in an opposite direction opposite to a predetermined direction, the rectified-input applying portion rectifying the motor control signal so as to limit the intermittent relative movement in the opposite direction, and applying the rectified motor control signal to the first electric motor,
and wherein the second motor control apparatus comprising:
a speed detector operable to detect a speed of a continuous relative movement of the recording medium and the printing head in a discrete manner;
a speed-control-error calculator operable to calculate a speed control error between the speed of the continuous relative movement detected by the speed detector and an externally commanded target speed value;
a speed-control-quantity calculator operable to calculate speed control quantities including a proportional control quantity proportional to the detected speed of the continuous relative movement or the speed control error, and an integral control quantity proportional to an integral of the speed control error;
a differential-control-quantity calculator operable to calculate a differential control quantity proportional to a derivative or an amount of change per unit time of the detected speed of the continuous relative movement or the speed control error;
a control-command-value determining portion operable to determine a control command value for operating the second electric motor to effect the continuous relative movement at the target speed value, on the basis of the speed control quantities and the differential control quantity, the second electric motor being controlled according to the control command value such that the detected speed of the continuous relative movement coincides with the target speed value; and
a differential-control-quantity compensating portion operable after expiration of a predetermined derivative effective time after each point of time at which the differential control quantity is updated by the differential-control-quantity calculator on the basis of the speed of the continuous relative movement detected by the speed detector, to compensate the differential control quantity such that the compensated differential control quantity is smaller than the differential control quantity as updated by the differential-control-quantity calculator, the derivative effective time being shorter than a period of detection of the speed of the continuous relative movement by the speed detector.
(51) An apparatus for controlling an electric motor provided to drive a movable object, comprising (a) a position controlling portion and (b) a speed controlling portion, wherein the position controlling portion includes:
a target inputting portion operable to input a target position for controlling a position of the movable object by the electric motor;
a detector operable to detect one of the position of the movable object or a motion of the electric motor;
a first signal generator operable to generate a first control signal on the basis of an output of the detector and the target value input by the target inputting portion;
an estimator operable to estimate a state quantity indicative of a state of the motion of the movable object, on the basis of the output of the detector and a motor control signal applied to the electric motor;
a second signal generator operable to generate a second control signal on the basis of the state quantity estimated by the estimator;
a motor-control-signal generator operable to generate the motor control signal on the basis of the first control signal and the second control signal; and
a rectified-input applying portion operable when the motor control signal requires the electric motor to be operated so as to operate the movable object in an opposite direction opposite to a predetermined direction, the rectified-input applying portion rectifying the motor control signal so as to limit the motion of the movable object in the opposite direction, and applying the rectified motor control signal to the electric motor,
and wherein the speed controlling portion includes:
a speed detector operable to detect a moving speed of the movable object in a discrete manner;
a speed-control-error calculator operable to calculate a speed control error between the moving speed detected by the speed detector and an externally commanded target speed value;
a speed-control-quantity calculator operable to calculate speed control quantities including a proportional control quantity proportional to the detected moving speed or the speed control error, and an integral control quantity proportional to an integral of the speed control error;
a differential-control-quantity calculator operable to calculate a differential control quantity proportional to a derivative or an amount of change per unit time of the detected moving speed or the speed control error;
a control-command-value determining portion operable to determine a control command value for operating the electric motor to move the movable object at the target speed value, on the basis of the speed control quantities and the differential control quantity, the electric motor being controlled according to the control command value such that the detected moving speed coincides with the target speed value; and
a differential-control-quantity compensating portion operable after expiration of a predetermined derivative effective time after each point of time at which the differential control quantity is updated by the differential-control-quantity calculator on the basis of the moving speed detected by the speed detector, to compensate the differential control quantity such that the compensated differential control quantity is smaller than the differential control quantity as updated by the differential-control-quantity calculator, the derivative effective time being shorter than a period of detection of the moving speed by the speed detector.